This invention relates to apparatus for repressurizing a tennis ball or other similar elastic sphere. More particularly, this invention relates to a pressurizer which punctures the ball with a hollow needle to inject a pressurizing gas. The needle automatically seals the puncture hole when it is withdrawn.
It is very desirable that the bounce characteristics of a tennis ball be uniform. The uniform bounce is provided by maintaining a constant pressure within the ball. Often, due to leaks in the ball, inadequate initial pressurization or diffusion through the wall of the ball, the pressure within the ball is below a minimum acceptable level, so that the ball is "dead" and unsuitable for play. In many cases, the ball can be restored to a useable condition by repressurizing it.
Several tennis ball repressurizing units are known in the art. Commonly, such devices insert a mixture of an inflating gas and adhesive into the ball through a hollow needle which punctures the wall of the ball. When the needle is withdrawn, the adhesive fills the puncture hole, and allegedly any other hole in the ball, thereby providing a tight seal of the puncture and any other gas leak in the ball. With such devices, however, some gas is likely to escape from the ball when the needle is withdrawn. Also, this sealing operation is not positively effective so that several attempts may be necessary to successfully seal the ball. Such pressurizers may be difficult to operate and require a considerable amount of maintenance to insure proper operation.
Other pressurizers are known which inject gas into the ball and insert a pre-cut plug in the puncture hole to seal it. This approach is time consuming since a separate plug is cut for each injection. Such plugs have a large cross-sectional area and, consequently, can be blown out of the puncture hole by the pressurized gas inside the ball. A further problem is that the plug disturbs the balance of the ball which causes it to wobble in flight.